1. Field of the Invention
The present invention relates to a valve unit for timely closing and opening a microfluidic channel, a microfluidic device including the valve unit, and a microfluidic substrate.
2. Description of the Related Art
Microfluidic channels are generally formed in a substrate (e.g., a lab-on-a-chip) used for performing, for example, biochemical reactions such as a lysis reaction and a polymerase chain reaction (PCR). A valve unit may be used to timely close and open such a microfluidic channel to regulate a fluid flow.
FIG. 1 is a plan view illustrating a conventional valve unit 10 disclosed in Robin Hui Liu et al., Anal. Chem. Vol. 76, pp. 1824-1831, 2004.
Referring to FIG. 1, the valve unit 10 includes a micro channel 12 forming a fluid passage, paraffin wax 20 preventing a flow of fluid (F) by closing the micro channel 12, and a wax chamber 15 adjacent to the paraffin wax 20. When it is necessary to move the fluid (F), heat (H) is applied to the paraffin wax 20 to melt the paraffin wax 20. As a result, the micro channel 12 is opened, and the fluid (F) can flow downward in the direction of the phantom arrow. Since the melted paraffin wax 20 is collected in the wax chamber 15, which is a widened area of the micro channel 12, the flow of the fluid (F) is not obstructed by the paraffin wax 20.
The valve unit 10 is called an open valve unit. That is, the valve unit 10 opens the initially-closed micro channel 12. In contrast, a close valve unit blocks an initially-opened micro channel. These known open valve unit and the close valve unit can either open or close microchannels, but are not be able to function to open and close a micro channel. In addition, a valve unit that can repeatedly open and close a micro channel has not been proposed yet. However, a substrate suitable for complex fluid reactions becomes quite bulky since several microfluidic chambers, channels, and open valve units and close valve units should be included in the substrate. Furthermore, the process of manufacturing the substrate is expensive and time-consuming.